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SOSORT 2022 Presentation Award Winners and Abstracts
PREDICTING SURGERY: ACCURACY OF THE BRAIST ENDPOINT DEFINITIONS AT 2-YEAR FOLLOW-UP
Lori Dolan1 , Stuart Weinstein1
1) University of Iowa Department of Orthopaedics and Rehabilitation
BrAIST defined “success” as Risser 4+ and Sanders 7 with a Cobb angle of <50 degrees, at point where future surgery would be unlikely, whereas surgery was expected in the “failed” group (>50 degrees prior to maturity). The prognostic accuracy of these endpoints has been questioned, as curves may continue to progress and surgery may still occur post-maturity. Thus, this study evaluated the predictive value of the BrAIST endpoints via a minimum 2-year radiographic/surgical follow-up.
What is the prognostic accuracy of the BrAIST definitions of success and failure?
The 272 subjects who completed BrAIST were eligible for follow-up if surgery occurred or at 2 years-post
BrAIST. The 25 BrAIST sites located and consented their own subjects. A pre-op or follow-up film was
submitted to the coordinating center for measurement. Progression was calculated as the difference
between the maximum Cobb angle at BrAIST exit and at follow-up. The surgery rate, and the mean length
of follow-up and curve progression were calculated. Prognostic accuracy was judged via the positive
predictive value (PPV, % surgery in the “failed” group) and negative predictive value (NPV,% no surgery in
the “success” group).
Of 272 subjects, we obtained documentation of surgery (date only or pre-op x-ray) or a new x-ray for
198(73%); 115 (85%)in the success group(SG)and 83(94%)in the failed group(FG). 15% of the SG group
underwent surgery compared to 94% of the FG. X-rays were available for 108 patients in the SG; of 83 (78%)
with no curve progression 8 had surgery; 25 curves progressed and 6 of these were operated on. The mean
pre-op Cobb angle was 48.1(range 40-58). Surgery in the SG occurred at an average of 2.5 years (range 6
mo to 4.2 years)after skeletal maturity. In this sample, the PPV was 94% (all but 6% of the FG had surgery)
and the NPV was 85% (15% of the SG had surgery). Overall, the BrAIST definitions predicted surgery
correctly in 89% of subjects.
BrAIST endpoints were set with future curve behavior in mind, yet surgery decisions not solely based on
Cobb angles. Curves as small as 40 degrees were operated in this sample, but one at 63 degrees was not.
Despite this variation, the BrAIST definitions of “success” and “failure” were correct for 89% of this sample
at a minimum of 2-year follow-up.
These endpoints therefore seem reasonable for use in future studies.
Disclosures (any Conflicts of Interest)
The authors have no conflicts of interest related to this work. The work was funded by the Joan and Phill
Berger Charitable Fund.
PREDICTION OF FUTURE CURVE ANGLE USING PRIOR VISIT INFORMATION IN PREVIOUSLY UNTREATED IDIOPATHIC SCOLIOSIS: NATURAL HISTORY IN PATIENTS UNDER 26 YEARS OLD WITH PRIOR RADIOGRAPHS
Eric Parent1 , Sabrina Donzelli2 , Maryna Yaskina5 , Alberto Negrini2 , Giulia Angela Antonela Rebagliati2 , Claudio Cordani3 , Stefano Negrini4
1) Department of Physical Therapy, University of Alberta, Edmonton, Canada 2) ISICO (Italian Scientific Spine Institute), Milan, Italy 3) IRCCS Galeazzi Orthopaedic Institute, Milan, Italy 4) Department of Biomedical, Surgical and Dental Sciences, University of Milan, IRCCS Istituto Ortopedico Galeazzi, Milan , Milan,Italy 5) Women & Children Health Resarch Institute, University of Alberta, Edmonton, Canada
Treatment selection for idiopathic scoliosis is informed by the risk of curve progression if untreated. Previous models predicting curve progression were limited by lack of validation, not including the full growth spectrum or including treated patients.
The objective was to develop and validate a model to predict future curve angles using clinical and radiographic data collected prior to an initial specialist consultation in idiopathic scoliosis.
This is an analysis from all 2317 patients with juvenile, adolescent or adult idiopathic scoliosis between 6 and 25 years old who were previously untreated and presented with at least one prior radiograph in addition to the one captured when entered prospectively in the database (since 2003) at first consult. We excluded those previously treated using scoliosis-specific exercises, bracing or surgery. All radiographs were re-measured by evaluators blinded to the predicted outcome: the maximum Cobb angle on the last radiograph while untreated. Linear mixed-effect models with random effects (SAS procedure Mixed) and maximum likelihood estimate were used to examine the effect of age at the baseline visit, sex, maximum baseline Cobb angle, retrospective Max Cobb angle, time (from baseline to prediction), Risser, and curve type on Cobb angle outcome. Interactions of baseline angle with time, quadratic time, and cubic time; of time with sex and time with Risser were also tested. A variance components structure was used in the covariance matrix. The models accounting for repeated measures from the same patient were evaluated by the smallest Akaike and Bayesian Information Criterion.
We included 2317 patients (83% were females) with 3255 total prior x-rays where 71% had 1, 21.1% had 2, 5.6% had 3, and 1.9% had 4 or more (with maximum 8). Mean age was 13.9±2.2yrs and 81% had AIS. Curve type was: 50% Double, 26% Thoracolumbar-Lumbar, 16% Thoracic, and 8% other. Cobb angle at first x-ray was 20±10o (0-80) vs 29±13o (6-122) at the specialist visit. Time between the first x-ray and the outcome clinic visit was 28±22mths. In the best model (Table 1), larger values of the following variables predicted larger future curves: Max Cobb Angle at baseline, Retrospective Max Cobb angle (on a previous x-ray), time to the target prediction (in half-years), and time cubed. Larger values on the following variables predicted a smaller future Max Cobb angle: Time squared, Baseline Risser, Baseline Age, Time*Risser interaction, and time*female sex interaction. Ten-fold cross-validation found a median error of 4.5o (worst interquartile range limits 1.8-8.9o, 54.9% within prediction interval, 84% within 10o of observed value). (Figure 2 and 3)
A novel internally validated model predicted future Cobb angle with good accuracy in non-treated idiopathic scoliosis over the full growth spectrum.
The model can help clinicians predict how much curves would progress without treatment at future timepoints of their choice using six simple variables. Predictions can inform treatment prescription or show families why no treatment is recommended. The non-linear effects of time account for the rapid increase in curve angle at the beginning of growth and the slowed progression after maturity.
Disclosures (any Conflicts of Interest)
No relevant COI disclosures.